Optical fibre and method of manufacturing an optical fibre

Abstract

The present invention relates to a method of manufacturing an optical fiber by carrying out one or more chemical vapor deposition reactions in a substrate tube, with the optical fiber exhibiting a low sensitivity to the hydrogen induced attenuation losses at a transmission wavelength of 1550 nm. The present invention furthermore relates to an optical fiber comprising a cladding layer and a light conducting core, which fiber has been obtained by using the present method.

1 . A method of manufacturing an optical fibre by carrying out one or more chemical vapour deposition reactions in a substrate tube, with the optical fibre exhibiting a low sensitivity to the hydrogen induced attenuation losses at a transmission wavelength of 1550 nm, which method comprises the following steps: 
 i) supplying one or more glass forming precursors, which may or may not be doped, to the substrate tube;    ii) supplying a stoichiometric excess amount of oxygen to the substrate tube;    iii) bringing about a reaction in the substrate tube between the reactants supplied in step i) and step ii) so as to deposit one or more layers of glass on the interior of the substrate tube;    iv) subjecting the substrate tube thus formed in step iii) to a collapsing treatment so as to form a preform; and finally    v) drawing an optical fibre from the preform formed in step iv) while heating, and subsequently cooling the same, characterized in that the vapour deposition reaction in step iii) is carried out in such a manner that the amount of oxygen supplied to the substrate tube in step ii) is maximally 3.5 times the stoichiometric amount.    
     
     
         2 . A method is according to  claim 1 , characterized in that the cooling process in step v) is carried out by cooling down the already drawn optical fibre at a temperature of at least 1000° C. for at least 0.08 seconds.  
     
     
         3 . An optical fibre comprising a cladding layer and a light conducting core, characterized in that it has been manufactured in accordance with  claim 1 .  
     
     
         4 . An optical fibre according to  claim 3 , characterized in that the amount of Cl in the light conducting core ranges between 500 and 3000 ppm.  
     
     
         5 . An optical fibre according to  claim 3 , characterized in that the amount of Cl in the light conducting core ranges between 1000 and 3000 ppm.  
     
     
         6 . An optical fibre according to  claim 3 , characterized in that the total attenuation losses, including the hydrogen induced attenuation losses at 1550 nm, are maximally 0.25 dB/km.  
     
     
         7 . An optical fibre comprising a cladding layer and a light conducting core, characterized in that it has been manufactured in accordance with  claim 2 .  
     
     
         8 . An optical fibre according to  claim 7 , characterized in that the amount of Cl in the light conducting core ranges between 500 and 3000 ppm.  
     
     
         9 . An optical fibre according to  claim 7 , characterized in that the amount of Cl in the light conducting core ranges between 1000 and 3000 ppm.  
     
     
         10 . An optical fibre according to  claim 7 , characterized in that the total attenuation losses, including the hydrogen induced attenuation losses at 1550 nm, are maximally 0.25 dB/km.  
     
     
         11 . An optical fibre comprising a light conducting core and a cladding layer, characterized in that the amount of Cl in the light conducting core ranges between 500 and 3000 ppm.